What are the steps I should take before using vacuum pump to seal the ac unit in my car?

Good evening, I am working on a ford focus 2005 zx4 2.0 cyc, and my concern I was wondering was other than sealing the air out of the A/C unit what else does the vacuum pump seal do? I can see you can add refrigerant and oil to your ac compressor, but my concern is for one its already blowing out hot air and since it is already blowing out hot air could that possible mean there is no refrigerant left in the ac unit and I do not have to get it flushed? If i still do before using the vacuum pump to seal ac unit and add refrigerant what all should I get done? If I take it to a shop to flush the lines, will the car still be derivable to destination that is about 0.6 miles away from the shop I will be getting the lines flushed at?Also when they say flush the lines what all specifically am I flushing? I am in the process of getting ready to change the AC Compressor because its going bad and am somewhat illiterate with cars, So me a student am asking for the best knowledge any of you wise teachers can give please thank you.

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  • M.
    Lv 7
    1 month ago
    Favourite answer

    Oh you have some very wrong ideas. 

    I don't understand your use of the word "seal".  A vacuum pump doesn't seal anything. 

    The vacuum pump removes moisture (humidity) and non-condensible gasses (oxygen, nitrogen, et cetera from our atmosphere) from the inside of the A/C system. 

    If there is dirt or debris inside the A/C system from a compressor failure, then you must open the system in various places and flush the dirt and debris and contaminated refrigeration oil out of the system. 

    You must also remove and replace the filter/drier which is often inside the accumulator, because you can't flush dirt and debris and oil out of the accumulator. 

    You must also remove the metering device (expansion valve or capillary tube) and either clean it of dirt and debris, or replace it. 

    Then with a new or rebuilt compressor, you inject the proper amount and type of new refrigeration oil into the system. 

    Then you assemble everything with new o-rings, and evacuate the system with a dual gauge set and a vacuum pump.  Then you shut all valves and let the system sit for 10 minutes and see if it holds the same vacuum reading.  That means there are no leaks. 

    You then charge as much of the required refrigerant as you can get into the evacuated, non-operating system by charging LIQUID into the HIGH side.  If you can't get all of the required refrigerant into the system, you close the valve and start the engine and run the A/C and charge the remaining refrigerant by sucking VAPOR into the LOW side. 

    You SHOULD be doing this with a teacher at your car so you do everything properly and in the right order. 

    WHY are you changing the compressor??  Please explain in detail. 

    Are you getting a NEW compressor, or a REBUILT compressor, or a USED compressor? 

    Everything must be fantastically clean or you will have problems. 

    Some of today's modern condensers do not flush well due to the way they are constructed.  If you have compressor failure debris in this kind if unflushable condenser, you will need to just get a NEW condenser. 

    If you don't understand EVERYTHING that I have explained, then you should NOT be doing this job.

    -Engine overhaul mechanic and general automotive mechanic since 1972 

    -A/C repair since 1980

  • 1 month ago

    How about letting a good AC mechanic fix your AC for you?! You don't have a clue and will waste more money guessing the way you are.

  • L.N.
    Lv 7
    1 month ago

    The AC system needs to be evacuated to remove moisture from the system any time it has been opened to replace a component or has completely lost the refrigerant charge. The low pressure causes any moisture to boil off where it can be pumped out. Leaving moisture in the system can allow it to create ice crystals that can plug the expansion orifice and it also reacts with refrigerant to produce acids which can corrode the system from the inside. Any time the system has been opened it is also common practice to replace the dryer. 

  • Dan
    Lv 5
    1 month ago

    Take the car to a shop that does a lot of a/c work and just let them do it for you. The learning curve here will cost you more than the repair.

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  • Anonymous
    1 month ago

    Time to invest in a service manual for your vehicle.

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